This invention relates to apparatus for supplying a plurality of different fluids, independently and simultaneously, to a bottom-blown or a top-and-bottom blown converter through a metal-refining gas injecting nozzle and an annular nozzle positioned therearound so as to inject cooling fluids to project the refining gas injecting nozzle, both nozzles being provided in the converter bottom.
Generally an, apparatus for supplying oxygen, hydrocarbon gas, nitrogen gas, cooling water and the like independently and simultaneously to a bottom- or top-blown converter includes a rotary joint coupled to the shaft of a trunnion ring supporting the converter. The rotary joint has a plurality of fluid passageways on the inside, thereof which lead to an injection nozzle or a converter cooling device by way of passageways in the trunnion shaft or pipes extending through sleeves fitted in the trunnion shaft.
Conventionally, a rotary joint for the top- and bottom-blown converters has been a simple assembly made up of a plurality of coaxially disposed pipes. As the number of injecting fluids increase, the number of coaxial pipes is increased accordingly. Usually about four pipes or so having different diameters, are coaxially extended. The difficulty of this arrangement is related to the need to keep the pipes of different diameters positioned around the same axis.
The conventional bottom-blown converters include two pipes, having different diameters, which are concentrically arranged inside the rotary joint to provide separate passageways for the refining oxygen and protective gas, and the pipings leading from the trunnion ring to the bottom are bifurcated so as to supply the fluids to the individual nozzles. With this design, in the event that a particular nozzle suffers extraordinarily rapid erosion, the flow rates and therefore the ratio of the oxygen to protective gas supplied to the nozzle in question cannot be controlled independently. Therefore, erosion of a single nozzle endangers the life of the entire bottom of the converter. Even if the bricks positioned around other tuyeres are still usable, the entire bottom must be replaced, causing a great economic loss.
If the supply of protective gas to an extraordinarily eroded nozzle is increased so as to provide more cooling, molten metal adheres to the exit end of the tuyers, thereby protecting the brick near the tuyers and lowering the wearing rate of the damaged nozzle. By this means, all tuyeres are allowed to wear uniformly. On the other hand, tuyere clogging is likely to occur, but this trouble can be eliminated by reducing the supply of protective gas and, thereby, melting away the excess metal or refractory material. To achieve this type of control, a flow-rate control valve must be provided in a protective gas conduit leading to each individual nozzle. However, flow-rate control valves cannot be provided close to the converter shell because of high temperatures associated therewith. Even if the valves were installed, they might possibly be damaged by the falling material. More over, it is very difficult to provide effective thermal protection to the electrical wiring etc. required for the valve operation. Accordingly, the flow-rate control valves must be positioned at a considerable distance away from the converter.
Another method commonly employed plugs the extraordinarily worn-down nozzle with metal or refractory material. But this method , of course, has its limit, because satisfactory refining cannot be accomplished when too many tuyeres are plugged. At any rate, even if this method is utilized an early bottom change is inevitable.